1. Field of the Invention
Exemplary embodiments of the present invention relate to a wireless transmitter for high mobility and high throughput and a mode control method thereof; and, more particularly, to an apparatus and method which decides an operation mode of a transmitter depending on a wireless network environment, a channel state, and a user's mobility and reconfigures the transmitter according to the decided operation mode.
2. Description of Related Art
In general, a wireless communication system has developed focusing on a data rate and mobility depending on the purpose of use.
For example, a 2G cellular terminal has been developed to use a service requiring a low data rate, such as a voice data service, while moving by car. Furthermore, a 3G cellular terminal based on a wideband code division multiple access (WCDMA) scheme or a high speed downlink packet access (HSDPA) scheme has been developed to use an Internet searching service or text data service requiring a low data rate while moving. Furthermore, the 3G cellular terminal has been developed to transmit and receive digital video or audio broadcasting by using digital multimedia broadcasting (DMB) technology, while moving by car.
Meanwhile, WiBro technology has been developed to use an Internet searching service or transmit and receive image signals requiring a low data rate, while moving by car. Furthermore, Wi-Fi technology has been developed to transmit high-quality multimedia video at a high data rate by using the IEEE 802.11a/b/g/n standard in a stationary state or low-mobility state. The IEEE 802.11n technology having a maximum data rate of 600 Mbps may transmit a high-quality image oh 100 Mbps or more, and maintain a service quality even in a stationary state or low-mobility state (for example, pedestrian speed).
The IEEE 802.11p technology of which the standardization is in progress for an intelligent mobile communication system may transmit data at a maximum data rate of 27 Mbps in a low-mobility state by using a bandwidth of 10 MHz in the 5.9 GHz frequency band, based on the IEEE 802.11a, and has been developed to transmit data requiring a low data rate even at a high movement speed of 200 km/h. Here, the IEEE 802.11a may transmit data at a maximum data rate of 54 Mbps by using a bandwidth of 20 MHz in the 5 GHz band, based on an orthogonal frequency division multiplexing (OFDM) scheme.
As such, the conventional wireless communication technology, which has developed focusing on the mobility and the high data rate, has the following problems.
Wireless communication terminal users want an environment in which a good quality of service is provided at a high movement speed. However, the currently-developed technologies do not satisfy such users' request. Specifically, the Wi-Fi technology guarantees a high throughput of 600 Mbps, but is not suitable for a mobile environment. Furthermore, the cellular technology may provide a voice communication service under a high-speed movement environment of 200 km/h, but may guarantee only a low data rate such as a voice data level.
Due to the limit of the Wi-Fi or cellular technology, the WiBro and IEEE 802.11p technology has been proposed. However, the WiBro and IEEE 802.11p technology provide a lower performance than the high data rate of the Wi-Fi technology and the high mobility of the cellular technology.
Recently, a demand for HD images or high-volume multimedia contents such as movies and music has been increasing. The maximum data rate of 27 Mbps in the IEEE 802.11p technology is not enough to provide a good quality of service to a plurality of users at the same time. That is, the IEEE 802.11p technology provides a data rate of 11 Mbps as the throughput of a media access control (MAC) layer when the channel state is favorable, and provides a much lower data rate while moving at a high speed or when a distance between terminals is large. Furthermore, as the mobility of a wireless terminal user increases in the IEEE 802.11p technology, the performance of the wireless terminal may be significantly degraded by a channel variation caused by a Doppler spread effect and a delay spread effect.